Process for making an elastomeric glove

ABSTRACT

A nitrile-rubber medical exam glove composed of a glove body which is a flexible layer of nitrile-butadiene rubber. The glove body has a chlorinated first surface forming a donning side of the glove body and an un-chlorinated second surface forming a grip side of the glove body. The elastomeric glove also includes a substantially uniform distribution of a release agent distributed over the un-chlorinated second surface of the glove body. The elastomeric glove has: (a) an average thickness of between about 0.03 to 0.12 mm in a palm region of the glove body as measured in accordance with ASTM D3767, procedure A; (b) an un-chlorinated second surface of the glove body characterized by a Surface Root Mean Square Roughness of from about 3.00 Î¼m to about 6.55 Î¼m; and (c) a failure rate of less than about 1 percent when the elastomeric glove is subjected to pinhole leak testing generally in accordance with ASTM D5151-06.

RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 13/060,198, filed on Apr. 29, 2011, which claimspriority to PCT International Patent Application No, PCT/IB2009/053758,filed Aug. 27, 2009; and U.S. Provisional Application No. 61/092,300,filed Aug. 27, 2008, each of which are incorporated by reference hereinin their entireties.

FIELD OF INVENTION

The present invention pertains to flexible synthetic rubber medical examgloves and methods of making such gloves.

BACKGROUND

The development of modern synthetic rubber materials have made possiblethe manufacture of a wide variety of elastomeric articles having varyingproperties of strength and chemical resistance. Among these articles aregloves designed for either industrial or medical uses. As safetyaccessories, industrial and medical gloves protect a user fromenvironmental hazards such as chemicals or pathogens. In particular,medical gloves contribute to sanitary hospital conditions by limitingexposure of patients to potentially infectious matter, and serve toprotect health professionals from disease transmission through contactwith body fluids.

Relatively thin and flexible industrial or medical gloves havetraditionally been made of natural rubber latex in a dipping process.The donning surface (i.e., the interior) of these gloves isconventionally coated with corn starch, talcum, or lypcopodium powder tolubricate the gloves, making them easier to don. In recent years,powder-free work gloves and medical gloves have largely replacedpowdered gloves because of changing needs and perceptions of gloveconsumers. For example, cornstarch or other powders can impede healingif it gets into tissue (as during surgery). Similarly, powders areunsuitable for clean rooms such as those used in the manufacture ofsemiconductors and electronics.

Glove consumers have been moving away from natural rubber gloves due, inpart, to an increasing rate of significant allergic reactions toproteins in natural rubber latex among health professionals as well asthe general population. The industry has increasingly moved to latexemulsions based on synthetic rubber materials. While hospitals,laboratories, or other work environments that use rubber gloves oftenwant to go “latex free” to better protect their workers, the higher costof non-latex products, such as nitrile rubber, often limits theirability to make the change. For example, nitrile rubber gloves may costtwo or more times the price of the natural rubber latex or vinyl-basedcounterparts. This fact has often caused purchasers in cost-sensitiveenvironments, such as many hospitals, either to switch to less expensivepolyvinyl chloride gloves or prevented them from switching to thesynthetic materials.

In addition to being more expensive, nitrile-butadiene rubber medicalexam gloves are typically stiffer and are perceived as much lesscomfortable to wear in comparison to similar gloves made from naturalrubber latex materials. For instance, natural rubber latex (NRL) medicalexam gloves typically require a stress of about 2.5 MPa (362.5 psi) tostretch to an elongation of about 300 percent of its originaldimensions. This often is referred to as the glove's 300 percentmodulus. Nitrile rubber medical exam gloves, on the other hand,typically require more than twice that amount of stress (˜6-8 MPa,˜870-1160 psi) to achieve the same 300 percent elongation. Whilepolyvinyl chloride medical exam gloves can be inexpensive, polyvinylchloride medical exam gloves are typically considered a lowerperformance choice. That is, polyvinyl chloride medical exam gloves aretypically stiffer and less elastic than even the conventional thickernitrile rubber medical exam gloves.

Several previous approaches to softening nitrile rubber medical examgloves involved strongly limiting or completely omitting zinc oxide andother materials capable of ionically crosslinking carboxylated nitrilerubber, such as those described in U.S. Pat. Nos. 6,031,042 and6,451,893. In addition to not yielding force-strain properties similarto those of comparable natural rubber medical exam gloves, this methodrequires higher curing temperatures, a need for higher levels of otherchemicals that may cause skin irritation, or may lead to processingdifficulties such as thickening of the nitrile latex before dipping.

Other approaches to making a nitrile-butadiene rubber medical exam glovemore comfortable, such as those described in U.S. Pat. Nos. 5,014,362and 6,566,435, have relied on stress relaxation over time and requireconstantly applied levels of strain to cause that relaxation orsoftening. Such determination measures are difficult to maintain and areconsidered impractical or economically unfeasible.

While it might seem that a practical solution to the expense ofconventional nitrile rubber medical exam gloves would be to make nitrilerubber medical exam gloves thinner than conventional nitrile rubbermedical exam gloves (e.g., about 0.11 to about 0.20 mm in thickness atthe palm region of the glove as measured generally in accordance withASTM D3767, procedure A), there are significant problems associated withmaking nitrile rubber medical exam gloves that are thinner thanconventional nitrile rubber medical exam gloves. A primary problem ispinhole formation which is sometimes referred to as “pinholes” or“pinhole defects. The lack of a thin nitrile rubber medical exam glovein the marketplace actually highlights the difficulties of economicallyand effectively solving these problems.

In the field of dipped rubber articles and in the field of breathable,stretched micro-porous films, a conventional solution is to pinholedefects is to utilize multiple thin layers of material. For example, PCTInternational Publication WO 1999/030904 A1 proposes in the manufactureof thin breathable films such as stretched micro-porous films that theuse of a multilayer film greatly reduces or eliminates the probabilityof an imperfection (i.e., a pinhole) in any one area of one layer of thefilm aligning with an imperfection (i.e., a pinhole) in the other layerof the film, thereby substantially increasing the probability that thematerial produced will meet ASTM barrier test requirements. However,forming multilayer thin films adds complexity and expense to themanufacturing process and defeats the cost advantages provided by makingan article thinner.

Similarly, U.S. Patent Application Publication No. 2008/0138723 A1discloses nitrile rubber latex formulations and a process to make amulti-layered elastic glove in which the thickness of the multi-layeredglove is between 0.01 mm and 0.3 mm. Such a multiple thin-layer dippingprocess to form thin multilayered gloves adds significant complexity andexpense to the manufacturing process and defeats the cost advantagesprovided by making an article thinner. Importantly, the lack of a thinmulti-layer nitrile rubber medical exam glove in the marketplaceactually highlights the difficulties of economically and effectivelysolving these problems.

Although comparatively inexpensive, polyvinyl chloride medical examgloves have a number of shortcomings. The shortcomings of polyvinylchloride medical exam gloves include: being relatively inelastic; havingrelatively low tensile strength; having relatively greater amounts ofpinhole defects; and leaching certain toxic components. Theseshortcomings can result in less comfort for the wearer, a weaker glovewith higher permeability or poorer barrier protection against somecommon chemicals, and harm to the user and/or environment. Polyvinylchloride medical exam gloves typically have a leakage percentage rate offrom about 16 percent to about 44 percent when subjected toconventionally accepted leak testing. Conventional nitrile rubbermedical exam gloves exhibit leakage percentage rates of less than 7percent, typically less than about 5 percent or even lower (e.g., lessthan 2 percent). Reports of this comparative testing may be found at,for example, Kerr L. N., Chaput M. P., Cash L. C., et al., 2004September Assessment of the Durability of Medical Examination Gloves,Journal of Occupational and Environmental Hygiene 1: 607-612; Kerr L.N., Boivin W. S., Chaput M. P., et al. 2002 September The Effect ofSimulated Clinical Use on Vinyl and Latex Exam Glove Durability. TheJournal of Testing and Evaluation 30 (5):415-420; Korniewicz D. M.,El-Masri M., Broyles J. M., et al., 2002 April Performance of Latex andNonlatex Medical Examination Gloves during Simulated Use. AmericanJournal of Injection Control, 30 (2):133-8; and Rego A., Roley L., 1999October. In-Use Barrier Integrity of Gloves: Latex and Nitrile Superiorto Vinyl. American Journal of Infection Control, 27 (5):405-410. Giventhat polyvinyl chloride is inherently a much weaker material in terms oftensile strength and is likely to have pinholes in the membrane,polyvinyl chloride medical exam gloves require the use of a greateramount of material to achieve the same level of strength and integrityas a nitrile rubber medical exam glove. In view of these and otherfactors, consumers are beginning to seek an alternative to polyvinylchloride gloves.

A need exists for an inexpensive, nitrile rubber glove that has goodbarrier properties at a cost that is less expensive than traditionalnitrile rubber gloves or comparable to polyvinyl chloride gloves.Moreover, a need exists for an inexpensive nitrile rubber medical examglove that can successfully provide the benefits of nitrile rubbermaterials while also providing pliability or softness like naturalrubber latex without the conditions required for softening caused bystress relaxation. The present invention provides a simple solution tothis need by means of a modified nitrile rubber-based synthetic polymerthat exhibits not only good chemical resistance, but also stretch andsilky tactile characteristics similar to natural rubber latex.

SUMMARY OF THE INVENTION

The present invention offers an economical solution to the needsoutlined above by providing a nitrile rubber glove, such as anitrile-rubber medical exam glove, that exhibits not only good chemicalresistance, but also force to stretch characteristics and silky tactilecharacteristics similar to natural rubber latex gloves, pinhole defectperformance similar to nitrile-rubber medical exam gloves ofconventional thicknesses, and relatively low cost similar to polyvinylchloride gloves.

The present invention relates to an elastomeric glove composed of aglove body which is a flexible layer of an elastomeric nitrile rubber(i.e., nitrile-butadiene rubber) formed from nitrile rubber latex (i.e.,nitrile-butadiene rubber latex). Desirably, the glove body is a singlelayer of an elastomeric nitrile-butadiene rubber. That is, the glovebody may consist of a single layer of an elastomeric nitrile-butadienerubber. In other words, the elastomeric glove may be composed of a glovebody that is a single layer of elastomeric nitrile-butadiene rubber andthe glove body may itself have applied layers or coatings of othermaterials such as release agents, donning layers, donning agents,silicone materials and the like. The glove body has a chlorinated firstsurface forming a donning side of the glove body and an un-chlorinatedsecond surface forming a grip side of the glove body. The elastomericglove also includes a substantially uniform distribution of a releaseagent, typically a metallic salt of a fatty acid, distributed over theun-chlorinated second surface of the glove body.

According to the invention, the elastomeric glove has: (a) an averagethickness of between about 0.03 to 0.12 mm in a palm region of the glovebody as measured in accordance with ASTM D3767, procedure A; (b) anun-chlorinated second surface of the glove body characterized by aSurface Root Mean Square Roughness of from about 3.00 μm to about 6.55μm; and (c) a failure rate of less than about 1 percent when theelastomeric glove is subjected to pinhole leak testing generally inaccordance with ASTM D5151-06. That is, when a sample of gloves (e.g.,100 or 1000 or even more) are tested in accordance with ASTM D5151-6which is a “pass-fail” test procedure, less than about 1 percent of thegloves in the sample will fail. For example, the elastomeric glovedesirably has a failure rate of less than about 0.5 percent when theelastomeric glove is subjected to pinhole leak testing generally inaccordance with ASTM D5151-06. As another example, the elastomeric glovedesirably has a failure rate of less than about 0.1 percent when theelastomeric glove is subjected to pinhole leak testing generally inaccordance with ASTM D5151-06.

Desirably, the un-chlorinated second surface of the glove body ischaracterized by a Surface Root Mean Square Roughness of about 3.00 μmto about 5.30 μm. In an aspect of the invention, the un-chlorinatedsecond surface of the glove body is characterized by a Surface Root MeanSquare Roughness of less than about 3.0 μm. According to the invention,the glove may have an average thickness as determined in accordance withASTM D3767, procedure A, ranging from about 0.025 or 0.03 mm to about0.15 mm, typically from about 0.04 mm to about 0.13 mm, or from about0.045 or 0.05 mm to about 0.08 or 0.10 mm. According to certainembodiments, the substrate has a thickness in the palm region of fromabout 0.045 mm to about 0.7 mm, or from about 0.05 mm to about 0.9 mm;or from about 0.05 mm to about 0.07 mm.

One feature of the present invention is that the glove body exhibits aforce-to-strain response from zero elongation to 300 percent elongation(F-300) of less than or equal to about 1.50 N at F-300 when tested inaccordance with ASTM D412-06. For example, the glove body desirablyexhibits a force-to-strain response when elongated from zero elongationto 300 percent elongation (F-300) that ranges from about 1.08 N to about1.45 N for a thickness of about 0.03-0.10 mm when tested in accordancewith ASTM D412-06. The glove body desirably exhibits a force-to-strainresponse during elongation from zero elongation to 400 percentelongation (F-400) of less than about 2 N at F-400 when tested inaccordance with ASTM D412-06, or the glove body exhibits aforce-to-strain response during elongation from zero elongation to 500percent elongation (F-500) of less than about 2 N at F-500 when testedin accordance with ASTM D412-06. In an aspect of the present invention,the glove body exhibits a force to break of less than about 6.0 N atabout 560 percent elongation to about 600 percent elongation of anoriginal dimension when tested in accordance with ASTM D412-06. Thesetensile strength characteristics are important for providing a practicaland useful glove, particularly when combined with the relatively lowglove thickness and the good performance in pinhole leak testinggenerally in accordance with ASTM D5151-06.

In another aspect of the invention, the glove body has a surface area tovolume ratio of greater than 84/cm. For example, the glove body may havea surface area to volume ratio of about 200/cm or greater. As anotherexample, the glove body may have a surface area to volume ratio betweenabout 150/cm to about 250/cm. As another example, the glove body mayhave a surface area to volume ratio of less than about 400/cm.

In yet another aspect of the invention, the un-chlorinated outer or“grip” surface of the glove body has a pore density of greater than orequal to about 800 pores per mm² as determined by optical imageanalysis. That is, the number of a concave dimples or pits (generallyreferred to as “pores”) located on the un-chlorinated outer (grip)surface of the glove body is greater than or equal to about 800 poresper mm² as determined by optical image analysis techniques. For example,the un-chlorinated outer or “grip” surface of the glove body may have apore density ranging from about 820 per mm² to about 1600 per mm² asdetermined by optical image analysis. It is contemplated that theun-chlorinated outer or “grip” surface of the glove body may have a poredensity greater than about 1600 per mm². In other examples, theun-chlorinated outer or “grip” surface of the glove body may have a poredensity that ranges from about 850 per mm² to about 1450 per mm². In yetother examples, the un-chlorinated outer or “grip” surface of the glovebody may have a pore density that ranges from about 900 per mm² to about1280 per mm².

The release agent distributed over the un-chlorinated second surface ofthe glove body is selected from metallic salts of a fatty acid,petroleum waxes with a melting point of less than about 200° C., naturalanimal waxes, or synthetic waxes. Desirably, the release agent is ametallic salt of a fatty acid such as metallic stearates. Even moredesirably, the release agent is a metallic stearate such as calciumstearate.

In an aspect of the invention, the elastomeric nitrile-butadiene rubberis a terpolymer of acrylonitrile, butadiene, and carboxylic acid inwhich the acrylonitrile polymer content is about 15 percent, by weight,to about 42 percent, by weight, the carboxylic acid content is betweenabout 1 percent, by weight and about 10 percent by weight, and theremaining portion of the terpolymer composition is butadiene. Forexample, the terpolymer may contain about 20 percent to about 40 percentacrylonitrile polymer, about 3 percent to about 8 percent carboxylicacid, and about 40 percent to about 65 or 67 percent is butadiene.Desirably, the terpolymer may contain about 20 percent to about 30percent acrylonitrile polymer, about 4 percent to about 6 percentcarboxylic acid, and the remaining balance is predominately butadiene(e.g., from about 64 percent to about 76 percent).

The present invention also encompasses a process for making anelastomeric glove. The process includes the following steps:

coating a surface of a mold with a coagulant solution and a releaseagent, the coagulant solution having a calcium ion concentration ofbetween about 3 percent and about 5 percent based on the weight ofcalcium ions in the coagulant solution;

partially drying the mold coated with the coagulant solution and waxyrelease agent;

immersing the partially dried mold into an nitrile-butadiene rubberlatex emulsion having a latex solids content of between about 52 percentand about 20 percent, by weight, for a dwell time of between about 7seconds and 15 seconds to form a layer of coagulated nitrile-butadienerubber latex on the mold surface;

removing the mold from the nitrile-butadiene rubber latex emulsion;

immersing the mold containing the coagulated nitrile-butadiene rubberlatex into an aqueous bath to remove excess calcium ions and then dryingthe coagulated nitrile-butadiene rubber latex to form a glove body onthe mold;

immersing the mold containing the glove body into a chlorinating bath tochlorinate an exterior surface of the glove body on the mold; and

removing the glove body from the mold by inverting the glove body suchthat the chlorinated exterior surface of the glove body forms aninterior surface of the glove and an un-chlorinated interior surface ofthe glove body forms an exterior surface of the glove.

According to the invention, the nitrile-butadiene rubber latex emulsionmay have latex solids content of between about 14 percent and about 20percent, by weight. Desirably, the nitrile-butadiene rubber latexemulsion may have a latex solids content of between about 15 percent andabout 19 percent. Even more desirably, the nitrile-butadiene rubberlatex emulsion may have a latex solids content of between about 16percent and about 18 percent. The dwell time that the partially driedmold is immersed into an nitrile-butadiene rubber latex emulsion may bebetween about 7 seconds and 13 seconds to form a layer of coagulatedpolymer on the mold surface. Desirably, the dwell time that thepartially dried mold is immersed into an nitrile-butadiene rubber latexemulsion may be between about 8 seconds and 12 seconds to form a layerof coagulated nitrile-butadiene rubber latex on the mold surface.According to an aspect of the invention, the mold coated with thecoagulant solution and waxy release agent is immersed into annitrile-butadiene rubber latex emulsion only a single time to form asingle layer of nitrile-butadiene rubber latex.

In an aspect of the invention, the nitrile-butadiene rubber latexemulsion is desirably one in which the elastomeric nitrile-butadienerubber is a terpolymer of acrylonitrile, butadiene, and carboxylic acidin which the acrylonitrile polymer content is about 20 percent, byweight, to about 30 percent, by weight, the carboxylic acid content isbetween about 4 percent, by weight and about 6 percent by weight, andthe remaining portion of the terpolymer composition is butadiene.

Additional features and advantages of the present invention will berevealed in the following detailed description. Both the foregoingsummary and the following description are merely representative of theinvention and are an overview for understanding the invention asclaimed.

BRIEF DESCRIPTION OF FIGURES

FIGS. 1A and 1B are scanning electron microscopy (SEM) photomicrographs,both at a linear magnification level of 200×, of the un-chlorinatedoutermost side of two different nitrile rubber medical exam gloves. Thesurface features of an exemplary elastomeric medical exam gloveaccording to the present invention is illustrated in FIG. 1A and thesurface features of a comparative, commercially available, nitrilerubber medical exam glove is illustrated in FIG. 1B.

FIGS. 2A and 2B are scanning electron microscopy (SEM) photomicrographs,at a linear magnification level of 1000×. FIG. 2A illustrates thecharacteristics of an exemplary surface of an elastomeric medical examglove according to the present invention. FIG. 2B illustrates thesurface features of a comparative, commercially available, nitrilerubber medical exam glove.

FIG. 3 is a schematic view illustrating an enlarged cross-section of anexemplary nitrile-butadiene rubber surface.

FIG. 4 is a graphical plot of water vapor transmission rate (WVTR)results for three different kinds of nitrile-butadiene rubber medicalexam gloves.

FIG. 5 is a comparative graph of the Force-Strain properties from fourdifferent medical exam gloves made from synthetic materials.

FIGS. 6A and 6B are scanning electron microscopy (SEM) photomicrographs,showing ‘raw’ and ‘detected’ pitting, respectively, for an exemplarysurface of an nitrile-butadiene rubber medical exam glove according tothe present invention.

FIGS. 7A and 7B are representative images showing ‘raw’ and ‘detected’pitting, respectively, for an exemplary surface of a comparative,commercially-available nitrile-butadiene rubber medical exam glove.

FIGS. 8A and 8B are histograms illustrating the frequency of poreshaving a specified equivalent circular diameter as determined by opticalimage analysis. FIG. 8A illustrates the frequency of pores having aspecified equivalent circular diameter as determined by optical imageanalysis for an exemplary surface of a nitrile-butadiene rubber medicalexam glove according to the present invention. FIG. 8B illustrates thefrequency of pores having a specified equivalent circular diameter asdetermined by optical image analysis for an exemplary surface of acomparative, commercially-available nitrile-butadiene rubber medicalexam glove.

FIG. 9 is a graph illustrating exemplary relationships between glovethickness and Water Vapor Transmission Rate for various samplenitrile-butadiene rubber medical exam gloves.

DETAILED DESCRIPTION OF THE INVENTION

A desirable attribute for elastomeric articles that are worn on the bodyis softness or pliability of the polymeric material. The presentinvention describes the creation of elastic articles, such as gloves,made from a nitrile polymer formulation. As used herein, the terms“elastic” or “elastomeric” generally refer to a material that, uponapplication of a force, is stretchable to an extended, biased length.Upon release of the stretching, biasing force, the material willsubstantially recover to near net shape or original dimensions.

Nitrile-butadiene rubber (commonly referred to as “nitrile rubber” or“NBR”) is a family of amorphous unsaturated copolymers of acrylonitrileand various butadiene monomers (1,2-butadiene and 1,3-butadiene). Thisform of synthetic rubber is generally resistant to aliphatichydrocarbons, such as fatty tissue, oils, and other chemicals.Nitrile-butadiene rubber has been used to create molded goods, footwear,adhesives, sealants, sponge, expanded foams, and floor mats. Itsresilience snakes conventional nitrile-butadiene rubber a good materialfor disposable gloves used in laboratory, cleaning, industrial work, andclinical situations. Conventional medical exam gloves made fromconventional nitrile-butadiene rubber generally are three times morepuncture-resistant, than conventional medical exam gloves made fromnatural rubber (i.e., formed from natural rubber latex) or polyvinylchloride.

Although gloves made from conventional nitrile-butadiene rubber are moreresistant to oils and acids than gloves made from natural rubber latex,traditionally gloves made from conventional nitrile-butadiene rubberhave inferior strength and flexibility in comparison to gloves that areessentially identical except for being made from natural rubber latex.The present invention utilizes a modified nitrile-butadiene rubberformulation and a modified glove manufacturing process to addressdrawbacks of gloves made from conventional nitrile-butadiene rubber. Themodified nitrile-butadiene rubber formulation and modified glovemanufacturing process is used to produce thin, flexible elastomericgloves that demonstrate unique physical characteristics. Of course, themodified nitrile-butadiene rubber formulation and a modified glovemanufacturing process may be adapted for the fabrication of otherdipped-goods such as, for example, balloons, membranes and the like.

As a disposable product, a nitrile-butadiene rubber glove made accordingto the present invention will have a mass that is at least about 40-50%less than a typical polyvinyl chloride-based glove of the same type(e.g., medical exam, household, or industrial) and size (i.e., small,medium, large, x-large). For example, a nitrile-butadiene rubber medicalexam glove according to the present invention that is made to theconventional size “M” or “Medium” will have a mass that is at leastabout 40 percent to about 50 percent less (or an even greater percentageless) than a typical polyvinyl chloride medical exam glove that is madeto the conventional size “M” or “Medium”.

As previously noted, various published reports describing comparativetesting of conventional polyvinyl chloride medical exam gloves andnitrile-butadiene rubber medical exam gloves show that polyvinylchloride medical exam gloves have a greater incidence of leakage. Giventhat vinyl is inherently a much weaker material in terms of tensilestrength and is likely to have pinholes in the membrane, vinyl-basedmedical exam gloves require the use of a greater amount of material toachieve the same level of strength and integrity as a nitrile-butadienerubber medical exam glove of the present invention. Thus, thenitrile-butadiene rubber medical exam gloves of the present inventioncontribute relatively less waste and have less environmental impactbecause they have substantially less mass than comparable polyvinylchloride medical exam gloves.

From a commercial viewpoint, the nitrile-butadiene rubber medical examgloves of the present invention are cost competitive with inexpensivepolyvinyl chloride medical exam gloves. That is, the thinnernitrile-butadiene rubber gloves of the present invention are moreaffordable than conventional nitrile-butadiene rubber gloves that arethicker products. The relatively lower cost of the thinnernitrile-butadiene rubber gloves of the present invention provides moreopportunities for consumers to switch from polyvinyl chloride gloves toa better performing nitrile-butadiene rubber glove (e.g., fewer pinholedefects and better stretch/tensile properties) without much adverseeconomic impact in addition to avoiding exposure to hazardous componentssuch as diethylhexylopthalate (DEHP) which can leach from polyvinylchloride gloves.

As noted above, manufacturers in the glove industry have not previouslydeveloped thinner, economical nitrile-butadiene rubber gloves because itwas generally believed that barrier properties of the nitrile-butadienerubber glove would be compromised by the thinness of the material andgiven the relative low cost of vinyl-based gloves, nitrile-butadienerubber gloves would be non-competitive in that segment of the market.Contrary to such beliefs, the present invention is directed to a thinnereconomical nitrile-butadiene rubber glove (i.e., an average thicknessbetween about 0.025 or 0.03 mm to about 0.15 mm, typically from about0.05 mm to about 0.13 mm, or from about 0.05 or 0.06 mm to about 0.08 or0.10 mm as determined in accordance with ASTM D3767, procedure A) withsatisfactory barrier performance and force to stretch properties.

For example, the elastomeric glove desirably has a failure rate of lessthan about 1 percent when the elastomeric glove is subjected to pinholeleak testing generally in accordance with ASTM D5151-06. This means thatwhen a sample of gloves (e.g., 100 gloves, 500 gloves, 1000 gloves, or10,000 gloves or even more) are tested in accordance with ASTM D5151-6which is a “pass-fail” test procedure, less than about 1 percent of thegloves in the sample will fail. As another example, the elastomericglove desirably has a failure rate of less than about 0.5 percent oreven less than about 0.1 percent when the elastomeric glove is subjectedto pinhole leak testing generally in accordance with ASTM D5151-06.

Although physical and chemical properties vary depending on thenitrile-butadiene rubber composition (the more acrylonitrile within thepolymer, the higher the resistance to oils but the lower the flexibilityof the material), the present invention combines soft, flexibleelastomeric characteristics with satisfactory levels of strength. In anaspect of the invention, these desirable properties are also combinedwith satisfactory levels of breathability as described or characterizedby conventional Water Vapor Transmission Rate (WVTR) testing.

The nitrile-butadiene rubber composition according to the presentinvention is desirably a random terpolymer of acrylonitrile, butadiene,and a carboxylic acid, such as a methacrylic acid. The compositionincludes, in terms of weight percent (wt. %) of the major components:about 15% to about 42% acrylonitrile polymer; about 1% to about 10%carboxylic acid, and the remaining balance is predominately butadiene(e.g., about 38% to about 75%). Typically, the composition is: about20-40% acrylonitrile polymer, about 3-8% carboxylic acid, and about40%-55% or 67% is butadiene. Particular compositions include aterpolymer of acrylonitrile butadiene and carboxylic acid in which theacrylonitrile content is less than about 35% and carboxylic acid is lessthan about 10%, with butadiene content being the remaining balance. Moredesirable composition can have a range of: about 20-30% acrylonitrilepolymer, about 4-6% carboxylic acid, and the remaining balance ispredominately butadiene. Processing or other component ingredients maybe either optional or present up to about 20% (i.e., 20 weight percent)of the total composition; typically in amounts ranging from about 0.1 toabout 17%. These other ingredients may include metallic oxides (e.g.,ZnO, MgO) in levels of about 0.25-10%, sulfur or other crosslinkingagents (e.g., peroxide, aziridine, acrylates) at levels of 0.001-3%, andaccelerators at a level of 0.25 to 2.0%. Any of the variousvulcanization accelerators may be use, including, but not limited tothiurams, dithiocarbamates, xanthates, guanidines, or disulfides.

The present invention can be adapted to make a variety of thin-walleddipped goods, such as medical examination or industrial gloves,balloons, condoms, probe covers, dental dams, finger cots, catheters,and the like. Alternatively, the nitrile-butadiene rubber can beincorporated as part of articles such as garments (e.g., shirts, pants,gowns, coveralls, headwear, shoe covers) or draping materials. Thegeneral process for making dipped elastic rubber products is well knownto those in the art, and will not be reviewed in detail herein. Forexample, U.S. Pat. No. 6,673,871, 7,041,367, or 7,178,171, the contentsof which are incorporated herein by reference, each describe exemplaryprocesses for making a dipped elastic rubber glove. However, the presentinvention also relates to a process for fabricating thin elastomericmembranes, films and articles that is an improvement over theconventional processes.

Using separate mechanisms, nitrile-butadiene rubber can be crosslinkedto generate desired levels of strength and chemical resistance. Thefirst mechanism of crosslinking occurs by ionically bonding carboxylicacid groups together using multivalent metal ions. These ions aretypically supplied through addition of zinc oxide to thenitrile-butadiene rubber latex emulsion. Typically, the physicalstrength and stiffness/softness properties of the polymer are sensitiveto this kind of crosslinking. The other crosslinking mechanism is bymeans of covalent bonding of the butadiene segments of the polymerusing, for example, sulfur and rubber accelerator catalysts, whichdevelops good chemical resistance properties.

In the present invention, the extent or amount and types of ioniccrosslinking can be controlled by regulating the content of all ionicmaterials during compounding or formulating of the nitrile-butadienerubber latex. The crosslinking of the carboxylic acid groups iscontrolled by the amount and type of ionic materials added to thenitrile-butadiene rubber latex before it us used to produce dippedarticles. The thickness of the article can be controlled by a variety ofmeans during the dipping process, such as coagulant concentration,manipulation of the length of time that the mold form dwells in or iscovered by the emulsion, temperature, or mechanical rotation or pivotingof the mold after withdraw from the dipping bath.

As with other dipped products, like balloons and condoms, elastomericnitrile-butadiene rubber gloves are often formed by first coating a moldsurface with a coagulant solution, for instance calcium nitrate, thendipping the mold into a polymer latex emulsion to cause gelation of thenitrile rubber over the mold surface. When parameters of a highpercentage of latex solids and/or a high concentration of the coagulantare used, the rubber particles gel very quickly to form a coagulatednitrile-butadiene rubber latex layer over the entire latex-coatedsurface of the mold. A latex emulsion having a solids content of about35 percent to about 40 percent, by weight, or greater can be referred toas being a relatively “high” solids content latex emulsion. Sometimesthe gelation can occur so quickly that the serum (water andaqueous-soluble materials) of the latex are forced out of the glove andappear as transparent drops. This is known as syneresis.

When conventional nitrile-butadiene rubber medical exam gloves areformed, a latex emulsion having conventional levels of latex solids(latex solids content of greater than about 21 percent, by weight up toabout 31 or 32 percent, by weight) and a conventional coagulant (i.e.,having a coagulating ion concentration of about 6 to 10 percent based onthe weight of the coagulation ion in solution) are needed to rapidlyform a relatively thick film of nitrile-butadiene latex on the glovemold. The coagulant is generally thought to react most quickly andeffectively with the portion of the nitrile-butadiene latex filmimmediately adjacent the layer of coagulant on the glove mold, and reactless thoroughly or effectively with the portion of the nitrile-butadienelatex film away from the layer of coagulant on the glove mold as thecoagulant ions are forced to migrate to penetrate further outward intothe thickness of the nitrile-butadiene latex film. This phenomenon isbelieved to result in a glove surface that is less smooth and may alsobe encountered when multiple thin layers are formed utilizing a multiplelatex dip process.

As the parameters of percent latex solids and coagulant concentrationare lowered, the gelation will tend to occur more slowly. If the dwelltime in the latex emulsion is constant, lowering the percent latexsolids and the coagulant concentration typically results in formation ofa thinner film layer. When a glove such as a medical exam glove (orother elastomeric membrane) is made according to the present invention,the glove is much smoother or can be characterized as “less rough” on atleast the un-chlorinated surface forming a grip side or exterior surfaceof the finished glove. This smoothness is readily perceptible toordinary individuals in an unaided comparison of gloves made accordingto the present invention and conventional nitrile-butadiene rubbergloves.

While the inventors should not be held to any particular theory, it isbelieved that such a smooth surface produced on a glove of the presentinvention is the result of using both a weak coagulant and a latexemulsion having a relatively low solids content in a single latexemulsion dip process which appears to cause the nitrile-butadiene latexfilm to gel more slowly on the mold. Given the nitrile-butadiene latexfilm layer is thinner than usual, NBR latex particles are believed toreact with the coagulant more efficiently and for a longer duration,which allows more time for the latex particles to become more tightlypacked together in the film layer. This more compact organization of thelatex particles is thought to result in a much smoother glove surfacewhen a single layer of nitrile-butadiene rubber latex is formed on themold in a single latex dip process.

The polymer latex solids in the nitrile-butadiene latex typically havean average particle size of about 0.08 μm to about 0.20 μm. According tothe invention, the nitrile-butadiene polymer latex has a relatively lowsolids content of between about 14 percent up to about 20 percent, byweight, of nitrile-butadiene polymer solids. Desirably, thenitrile-butadiene polymer latex has a solids content of between about 15to about 18 percent, by weight.

During the dip process, the glove former is dipped in thenitrile-butadiene rubber latex for a dwell time duration of about 13seconds or less. Desirably, the dwell time of the single dip is betweenabout 12 seconds and 7 seconds. Even more desirably, the dwell time isbetween about 7 to 10 seconds.

According to an aspect of the present invention, the particular solidscontent of the nitrile-butadiene rubber latex influences the associatedpercentage amount of coagulant applied in the manufacture process. Inother words, the amount of coagulating ion present on the glove moldgenerally corresponds proportionately to the latex solids content in aratio of about 1:4, however slightly more or less of either may be useddepending on the duration of the dwell time of the mold in the latexemulsion. For example, a coagulant solution containing from about 9 toabout 12 percent, by weight, calcium nitrate would typically provideapproximately from about 3.6 to about 4.8 percent, by weight, calciumions in the solution. The coagulant ion is thought to transfer to theglove mold at the same concentration it is in solution. Utilizing thecoagulating ion concentration to latex solids concentration ration ofabout 1:4 for this example coagulant solution, the nitrile-butadienerubber latex should have a solids content of from about 14 to 19percent, by weight.

According to the present invention, the coagulated substrate or film hasa coating of a release agent over at least a portion of an outer surface(or grip side in a glove) of the substrate. The release agent is in theform of a “waxy” material and is used in the fabrication of apowder-free dipped article. The release agent is typically a low-meltingorganic mixture or compound of high molecular weight, solid at roomtemperature and generally similar to fats and oils except that itcontains no glycerides. For example, the release agent can be: ametallic stearate (e.g., calcium stearate, zinc stearate); a petroleumwax with a melting point of less than about 200° C. (e.g., melting pointbetween about 135° C. to about 180° C.) which can be in the form ofparaffin waxes, microcrystalline waxes, or petroleum jelly; a naturalanimal/insect wax such as bee's wax; or a synthetic wax (e.g.,polyethylene waxes). Desirably, the release agent is a metallic stearateparticularly calcium stearate. Generally speaking, the release agent isemulsified in the coagulant solution and is present at levels of aboutone percent by weight or less.

During processing of the nitrile-butadiene rubber glove according to thepresent invention, only one side of the layer of coagulatednitrile-butadiene latex forming the glove body on the glove former issubjected to halogenations (i.e., chlorination), if chlorination is usedat all. That is, the glove body will have a chlorinated first surfaceforming a donning side of the glove body and an un-chlorinated secondsurface forming a grip side of the glove body. After forming, the gloveis cured and vulcanized and may be rinsed multiple times to remove anyexcess coagulant and accelerators that may be present on or in thematerial.

Using the protocol described in ASTM D3767, procedure A, glove membranethicknesses are measured. The elastomeric substrate can have an averagethickness of about 0.025 or 0.03 mm to about 0.15 mm, typically fromabout 0.05 mm to about 0.13 mm, or from about 0.5 or 0.06 mm to about0.08 or 0.10 mm. When made into a glove, according to certainembodiments, the substrate has a thickness in the palm region of about0.05 mm to about 0.09 mm. More desirably, the substrate has a thicknessin the palm region of about 0.05 mm to about 0.07 mm.

The gloves made using the current invention are less bulky and morepliable to wear, providing greater comfort compared to conventionalnitrile-butadiene rubber gloves, and further can lead to cost savings inthe manufacture process and ultimately to the consumer. With a thinnermaterial, the wearer also enjoys greater tactile sensation in the handand finger tips than compared with regular gloves.

Surface Features

FIGS. 1A and 1B are scanning electron microscopy (SEM) photomicrographs,both at a linear magnification level of 200×, of the un-chlorinatedoutermost side of two different nitrile-butadiene rubber medical examgloves. The side of the glove illustrated in she photomicrographs is theside adjacent the former during the dipping process and which becomesthe outermost side as the glove is inverted when it is removed from theformer. More particularly, the surface features of an exemplaryelastomeric nitrile-butadiene rubber glove according to the presentinvention is illustrated in FIG. 1A. The exemplary elastomericnitrile-butadiene rubber glove according to the present invention isoccasionally referred to as a “Nitrile A” glove.

The surface features of an exemplary elastomeric medical exam gloveillustrated in FIG. 1B are from a Kimberly-Clark® Safeskin® PURPLENitrile® medical exam glove available from Kimberly-Clark Corporation.The Kimberly-Clark® Safeskin® PURPLE Nitrile® medical exam glove may bereferred to a “Nitrile C” glove.

As can be seen from these photomicrographs, the nitrile-butadiene rubberglove according to the present invention has greater surface “pitting”in the form of a distribution of small, numerous surface pores than theKimberly-Clark® Safeskin® PURPLE Nitrile® medical exam glove.

FIGS. 2A and 2B are scanning electron microscopy (SEM) photomicrographs,at a linear magnification level of 1000×. FIG. 2A illustrates thecharacteristics of an exemplary surface of an elastomeric gloveaccording to the present invention. FIG. 2B illustrates the surfacefeatures of the Kimberly-Clark® Safeskin® PURPLE Nitrile® medical examglove. As shown in these more detailed views of the surfaces of eachglove, the nitrile-butadiene rubber glove according to the presentinvention has greater surface “pitting” in the form of a distribution ofsmall, numerous surface pores than the Kimberly-Clark® Safeskin® PURPLENitrile® medical exam glove. These small, numerous surface pores do notappear to affect the water vapor transmission rate (WVTR) performance byincreasing the increasing the WVTR performance. Moreover, the small,numerous surface pores do not adversely affect tactile perception.Generally speaking, the pores are “concave” and are essentially belowthe general level of the surface. At least for this reason, the small,numerous surface pores do not appear to be sensed by touch. To anordinary wearer of a glove according to the present invention, thetactile sensation and texture of at least the un-chlorinated exterior or“grip side” glove is more “silky” or “smooth” than that of aconventionally manufactured nitrile rubber glove. The small, numeroussurface pores appear to have little or no adverse effect regarding atactile perception of roughness. That is, the surface pores as generallyillustrated in FIG. 2A at least at the un-chlorinated exterior or “gripside” of the glove of the present invention are undetectable to anordinary user and do not interfere with or degrade the generally “silky”or “smooth” tactile sensation experienced by a user in comparison to asimilarly un-chlorinated exterior or “grip side” of a conventionalnitrile-butadiene rubber glove.

The generally “silky” or “smooth” surface of at least the un-chlorinatedexterior or “grip side” of the glove of the present invention can becharacterized or expressed quantitatively by any number of ways known tothose skilled in the art using well-known non-contact opticalprofilometry techniques. As an example, two-dimensional smoothness canbe expressed in terms of the roughness average (Ra), the root meansquare roughness (Rq), the maximum height of the profile (Rt), or theaverage maximum height of the profile (Rz).

Although the gloves of the present invention are perceived as verysmooth, on a microscopic level the surface features of the gloves have asurface texture, such as illustrated schematically and not necessarilyto scale in FIG. 3, which represents an enlarged cross-section of anexemplary surface profile for a surface such as, for example, a surfaceof a glove.

Roughness Average is measured in micrometers and the Ra measurement fora sample length “L” is the mean height of the surface profile (peaks andinverted valleys). Smoother surfaces have fewer peaks and valleys orless variability in the heights or the peaks and/or the depths of thevalleys. Referring again to FIG. 3, Curve “C” represents atwo-dimensional profile of a section of a surface for a sample length“L”. Line “D” is a representative line such that the sum of the surfacesS above and below line D is equal and is sometimes referred to as themean line. Ra is the arithmetic average of the distances of height “h”of the curve “C” from the line “D”. In other words, Ra is the meanheight calculated over sample length.

Root Mean Square (RMS) roughness is designated as the parameter Rq. Itis the root mean square average of the measured height deviations usedin the calculation of Ra. Rq is more sensitive to large excursions fromthe mean line than Ra, which is an arithmetic average. If a surface hasa profile that contains no large deviations from the mean surface level,the values of Ra and Rq will be similar. If there are appreciablenumbers of large bumps or holes, the largest values of the profileheight function will dominate the surface characteristics and Rq will belarger than Ra.

Rt is the maximum peak-to-valley height in the sampling length. Rz isthe average of the greatest peak-to-valley separations and is known asthe 10-point height parameter which is the average height differencebetween the five highest peaks and the five lowest valleys within thesampling length.

The roughness of the grip side surfaces of sample medical exam gloveswere measured using non-contact optical profilometry techniques tocreate a three-dimensional representation of the surfaces as explainedin further detail in the Experimental section of this document.Three-dimensional surface profilometry maps were exported from theprofilometer for analysis with surface topography software as explainedin further detail in the Experimental section of this document. Theuniversal roughness parameters Sa (Surface Average Roughness) and Sq(Surface Root Mean Square Roughness) were calculated. The totalz-envelope height (St) was also measured. St is not generally used orrecognized as a measure of texture but is a simple dimensionalindicator.

Sa (Surface Average Roughness) is the three-dimensional analogue of thetwo-dimensional roughness parameter Ra described above. Sq (Surface RootMean Square Roughness) is the root mean square calculation which is moresensitive to larger deviations as generally explained above. Sq adispersion parameter defined as the root mean square value of thesurface departures within the three-dimensional sampling area and issometimes referred to as the “Root-Mean-Square Deviation of the Surface”or the “Surface RMS Roughness”. These roughness parameters areuniversally recognized and may be used to define differences.

Three-dimensional surface texture is composed of three components:roughness, waviness and form. With respect to the nitrile-butadienegloves of the present invention, roughness is a function the fabricationprocess and includes surface irregularities that result from coagulationof the polymer latex and fabrication process. Waviness is the componentthat is superposed by roughness; and form is the overall shape of thesurface minus contributions from roughness and waviness. See “ExploringSurface Texture” by H. Dagness (ISBN 0 901920 07 X) published by RankTalylon Hobson Ltd., U.K. Data can be filtered using a waviness orroughness filter (essentially low and high pass filters) prior tocalculation of roughness. Filters are selected based on what aspect of asurface is most important to measure (for example a speckle structure ina paint finish or longer wavelength ripples, etc.). The data reportedherein were not filtered prior to calculation of Sa (Surface AverageRoughness) and Sq (Surface Root Mean Square Roughness) since there wasno basis to do so because the samples of glove materials were flat.

Table 1 below lists the results of the profilometric analysis for asample un-chlorinated “grip-side” or exterior surface of anitrile-butadiene rubber glove according to the present invention(referred to as the Nitrile A glove) and for a sample un-chlorinated“grip-side” or exterior surface of a Kimberly-Clark® Safeskin® PURPLENitrile® medical exam glove available from Kimberly-Clark Corporation(referred to as the Nitrile C glove). These three-dimensional roughnessresults are based solely on the analysis of the three-dimensionalrepresentation of the surfaces created by non-contact opticalprofilometry techniques.

TABLE 1 Comparative Summary of Surface Roughness Material type Sample Sa(μm) Sq (μm) St (μm) Nitrile A 1 2.04 3.63 60.6 2 2.17 4.32 63.0 Average2.10 3.98 61.8 Nitrile C 1 4.67 10.6 69.0 2 3.20 7.51 66.8 Average 3.949.06 67.9 Ratio Nitrile C/Nitrile A 1.87 2.27 units = micrometers (μm)Sa = Surface Average Roughness Sq = Surface Root Mean Square RoughnessSt = z-envelope height

The profilometric results indicate that the grip side of Nitrile A glovehas significantly lower average roughness than the grip side of NitrileC glove. As can be seen from the calculated “Ratio Nitrile C/Nitrile A”of the average of two samples, the grip side of the Nitrile C glove hasa Surface Average Roughness (Sa) that is approximately 87% rougher thanthe grip side of the Nitrile A glove based. As can also be seen from thecalculated “Ratio Nitrile C/Nitrile A” of the average of two samples,the Nitrile C glove has a Surface Root-Mean-Square Roughness (Sq) is227% greater than of Nitrile A. These differences are believed to bemeaningful such that the Nitrile A glove has a noticeably smoothersurface that that is readily detected by an ordinary person who handlesor uses the glove.

Generally speaking, the Surface RMS Roughness (Sq) of at least theun-chlorinated grip side of the gloves according to the presentinvention (i.e., Nitrile A gloves) may have a value ranging from about3.00 μm to about 6.55 μm. Desirably, the Surface RMS Roughness (Sq) ofat least the un-chlorinated grip side of the gloves according to thepresent invention (i.e., Nitrile A gloves) may have a value of less thanabout 5.20 or 5.30 μm. More desirably, the Surface RMS Roughness (Sq) ofat least the un-chlorinated grip side of the gloves according to thepresent invention (i.e., Nitrile A gloves) may have a value of less thanabout 3.5 or 3.0 μm. In some embodiments, the Surface RMS Roughness (Sq)of at least the un-chlorinated grip side of the gloves according to thepresent invention (i.e., Nitrile A gloves) may have a value of below 2.0μm or even lower. It is contemplated that Surface RMS Roughness (Sq)values may be as low as about 1.0 or 0.5 μm.

In addition to having at least an un-chlorinated grip side surface thatmay readily be characterized by non-contact optical profilometryanalysis as smoother than other nitrile-butadiene rubber gloves, a glovemade according to the present invention also has a distribution oflarger and more numerous pores on at least an un-chlorinated grip sidesurface of the glove as generally illustrated in FIG. 2A. Thisdistribution of larger and more numerous pores on at least anun-chlorinated grip side surface of the glove may readily becharacterized by optical image analysis as explained in further detailin the Experimental section of this document. For the purposes of thepresent invention, the term “pore” or “pores” refers to small opening inthe surface of a nitrile-butadiene glove surface that does not typicallypass through the entire material of the glove.

As discussed above, these small, numerous surface pores do not appear toaffect the water vapor transmission rate (WVTR) performance byincreasing the increasing the WVTR performance. Moreover, the small,numerous surface pores do not adversely affect tactile perception.Generally speaking, the pores are “concave” and are essentially belowthe general level of the surface. At least for this reason, the small,numerous surface pores do not appear to be sensed by touch.

Generally speaking, it is believed that the release agent in the form ofa waxy material that is coated on the glove form or glove mold, such asthe stearate from a powder-free calcium stearate coagulant distributesitself with a relatively great uniformity on the surface of the glove.Evidence of this uniformity is that no build-up or other poor releaseeffects are observed on the molds after significant use. As discussedabove, the present invention provides a longer gelation time in whichNBR latex particles are believed to react with the coagulant moreefficiently and for a longer duration allowing more time for the latexparticles to become more tightly packed together in the film layer.While the inventors should not be held to any particular theory ofoperation, the effect of the distribution of release agent on thenitrile-butadiene latex film layer is thought to work in combinationwith the longer gelation time and the more compact organization of thelatex particles to result in a much smoother surface when a glove when asingle layer of nitrile-butadiene rubber latex is formed on the mold ina single latex dip process, as well as to result, in a distribution oflarger and more numerous pores on at least an un-chlorinated grip sidesurface of the glove that may readily be characterized by optical imageanalysis.

Generally speaking, it is believed that the elastomericnitrile-butadiene medical exam gloves of the present invention having adistribution of pores with an average diameter that is larger and moreevenly spaced than other nitrile-butadiene medical exam gloves conveysan advantage in consistent flexibility and/or drape. The dimpled ordiscontinuous surface created by the pores, is thought to help enablethe material to fold more easily. Further, this feature can be used tobetter retain surface active agents such as antimicrobial agents,fragrances, scents, or the like.

The un-chlorinated outer or “grip” surface of the glove body of thepresent invention has a pore density of greater than or equal to about800 pores per mm² as determined by optical image analysis. That is, thenumber of a concave dimples or pits (generally referred to as “pores”)located on the un-chlorinated outer (grip) surface of the glove body isgreater than or equal to about 800 pores per mm² as determined byoptical image analysis techniques. For example, the un-chlorinated outeror “grip” surface of the glove body may have a pore density ranging fromabout 820 per mm² to about 1600 per mm² as determined by optical imageanalysis. It is contemplated that the un-chlorinated outer or “grip”surface of the glove body may have a pore density greater than about1600 per mm². In other examples, the un-chlorinated outer or “grip”surface of the glove body may have a pore density that ranges from about850 per mm² to about 1450 per mm². In yet other examples, theun-chlorinated outer or “grip” surface of the glove body may have a poredensity that ranges front about 900 per mm² to about 1280 per mm². Incomparison, a similarly un-chlorinated exterior or “grip side” of athicker nitrile-butadiene rubber glove such as, for example, aKimberly-Clark® Safeskin® PURPLE Nitrile® medical exam glove typicallyhas a pore density of less than 700 pores per mm² as determined byoptical image analysis.

In a comparative measurement of a representative sample of theun-chlorinated outer or “grip” surface of the glove body of the presentinvention versus the un-chlorinated outer or “grip” surface of arepresentative thicker and more conventionally producednitrile-butadiene rubber glove (i.e., a Kimberly-Clark® Safeskin® PURPLENitrile® medical exam glove), the glove of the present invention has apore density of 1153 pores per mm², which is nearly twice (˜1.71×) thepore density of the comparative glove surface at 673 pores per mm². Thepores in the present substrate are generally more evenly distributed ina given area of the substrate surface than in the comparable surface(i.e., un-chlorinated outer or “grip” surface) of conventionalnitrile-butadiene rubber gloves. The average pore size in the glove ofthe present invention is also about 16% larger than that in thecomparable surface of conventional nitrile-butadiene rubber gloves. Thegloves of the present invention have pores displaying an average“equivalent circular diameter” as determined by optical image analysisof between about 5 micrometers (μm) and about 6.5 micrometers (μm) inthe present substrate, as compared to an average equivalent circulardiameter of about 4.0 μm to about 5.6 μm in the comparable surface ofconventional nitrile-butadiene rubber gloves.

Moisture Vapor Transmission Rate

Samples of three different types of nitrile-butadiene rubber gloves weretested to measure Water Vapor Transmission Rate as explained in moredetail below in the Experimental section of this document. As usedherein, the “Water Vapor Transmission Rate” (WVTR) generally refers tothe rate at which water vapor permeates through a material as measuredin units of grams per meter squared per 24 hours (g/m²/24 hrs) or(g/m²/day). The moisture vapor transmission rates of the three gloveswere tested in accordance with ASTM Standard E96-80. Other techniquesthat are well-suited for materials thought to have a WVTR of up to about3,000 grams per meter squared per 24 hours (g/m²/24 hrs) may be used,such as, for example the test procedure standardized by INDA(Association of the Nonwoven Fabrics Industry), number IST-70.4-99,entitled “STANDARD TEST METHOD FOR WATER VAPOR TRANSMISSION RATE THROUGHNONWOVEN AND PLASTIC FILM USING A GUARD FILM AND VAPOR PRESSURE SENSOR”which may be earned out utilizing, for example, a PERMATRAN-W Model 100Kmanufactured by Mocon/Modern Controls, Inc., Minneapolis, Minn.

The three different types of nitrile-butadiene rubber gloves were testedto measure Water Vapor Transmission Rate. The three different types ofgloves are as follows:

(1) A nitrile-butadiene rubber glove according to the present inventionwhich had a thickness in the palm region of the glove of approximately0.05 millimeters as determined by ASTM D3767, procedure A (referred toas “Nitrile A glove” or just “Nitrile A”). This glove has anun-chlorinated grip side surface and is manufactured as discussed aboveusing a powder-free coagulant and a release agent in the form of calciumstearate.

(2) A Kimberly-Clark® STERLING® nitrile medical exam glove (anitrile-butadiene rubber glove which had a thickness in the palm regionof the glove of approximately 0.08 millimeters as determined by ASTMD3767, procedure A (referred to as “Nitrile B glove” or just “NitrileB”). This glove also has an un-chlorinated grip side surface and ismanufactured as using a powder-free coagulant and a waxy release agentin the form of a metallic stearate.

(3) A Kimberly-Clark® Safeskin® PURPLE Nitrile® medical exam glove (anitrile-butadiene rubber glove) available from Kimberly-ClarkCorporation which had a thickness in the palm region of the glove ofapproximately 0.11 millimeters as determined by ASTM D3767, procedure A(referred to as “Nitrile C glove” or just “Nitrile C”). This glove alsohas an un-chlorinated grip side surface and is manufactured as using apowder-free coagulant and a waxy release agent in the form of a metallicstearate.

The individual test results, along with the average and standarddeviation for five sub-samples of each glove type are provided in Table2A below. This data is shown graphically in FIG. 4, which is a graphicalplot of water vapor transmission rate (WVTR) results for the threedifferent kinds of nitrile-butadiene rubber gloves substrates identifiedabove. As shown in Table 2A and in FIG. 4, the comparativenitrile-butadiene rubber gloves (i.e., Nitrile B glove and Nitrile Cglove) have an average Water-Vapor Transmission Rate (WVTR) of less thanabout 250 or 275 g/m²/day. The thin, nitrile-butadiene gloves accordingto the present invention (i.e., the Nitrile A gloves) exhibit an averageWater-Vapor Transmission Rate (WVTR) of more than at least about 285g/m²/day and may exhibit values of up to about 550 g/m²/day. Accordingto the present invention, the average WVTR for Nitrile A glovesgenerally is at least about 300 g/m²/day, and may exhibit values of upto about 460 or 480 g/m²/day. The WVTR for Nitrile A glove samples mayhave an average WVTR between about 310 or 315 g/m²/day to about 400 or430 g/m²/day. According to certain samples, the average WVTR may rangefrom about 317±3 g/m²/day to about 345±3 g/m²/day.

TABLE 2A WVTRs for Three Nitrile-butadiene rubber glove Types ASTM 2437Water Vapor Transmission Rate (g/m²/day) Sample Nitrile A Nitrile BNitrile C 1 338 280 179 2 316 278 182 3 342 242 203 4 329 247 213 5 316263 161 Avg. 328.2 262.0 187.6 Std Dev 11 28 21

From Table 2A, one can see that Nitrile A gloves have the highestaverage WVTR and are considered the most “breathable” of the three glovetypes tested. Generally speaking, when an ordinary user wears theNitrile A continuously for any length of time, particularly for morethan about 5 minutes, the Nitrile A gloves tend to feel cooler thancomparative nitrile-butadiene rubber gloves. This feeling of coolness isreadily noticeable to ordinary users through their unaided sensation ofskin surfaces of their hand that are covered by the glove.

The Water-Vapor Transmission Rate (WVTR) is a phenomenon that isinfluenced or impacted by many variables, including the thickness of thematerial through which water vapor must pass. If all conditions aregenerally similar, the WVTR would be expected to be relativelypredictable and proportional for similar materials having differentthicknesses. In this case, the nitrile-butadiene rubber material of thethree different gloves are considered to be generally similar materials(i.e., all are medical exam glove grade nitrile-butadiene rubber formedfrom nitrile-butadiene rubber latex) and one of ordinary skill wouldexpect the WVTR for the Nitrile A glove and the Nitrile B glove to bepredictable based on the WVTR performance of the Nitrile C glove.

The WVTR performance for the Nitrile A glove and the Nitrile B glove maybe predicted from the actual WVTR performance of the Nitrile C glove andthe relative thicknesses of the Nitrile C glove and the Nitrile A gloveor Nitrile B glove. For example, for the Nitrile B glove, this wasaccomplished by the following formula:Nitrile B WVTR=[Nitrile C thickness (mm)/Nitrile B thickness(mm)]×Nitrile C WVTR

Table 2B summarizes the WVTR data for the three type of nitrilematerial, as above, as actually observed and as predicted from theNitrile C glove. FIG. 9 presents the data in graphical form.

TABLE 2B WVTR for Three Nitrile-Butadiene Rubber Glove Types SampleThickness WVTR actual WVTR Predicted Glove (mm) (g/m²/day) (g/m²/day)Nitrile A 0.05 324 411 Nitrile B 0.08 262 257 Nitrile C 0.11 187 —

As shown in Table 2B, the WVTR for a glove made according to the presentinvention is less than proportional to its thickness in comparison tothe other nitrile-butadiene rubber gloves. For example, a comparison ofthe actual WVTR for the Nitrile A glove with its predicted WVTR(calculated from the thickness and actual WVTR of the Nitrile C glove)reveals that the actual WVTR for Nitrile A glove is about 23% less thanpredicted—based on glove thickness.

Table 2C summarizes the WVTR data for the three type of nitrilematerial, as above, as actually observed and as predicted from theNitrile B glove.

TABLE 2C WVTR for Three Nitrile-Butadiene Rubber Glove Types SampleThickness WVTR actual WVTR Predicted Glove (mm) (g/m²/day) (g/m²/day)Nitrile A 0.05 324 419 Nitrile B 0.08 262 — Nitrile C 0.11 387 191

A comparison of the actual WVTR for the Nitrile A glove with itspredicted WVTR (calculated from the thickness and actual WVTR of theNitrile B glove) reveals that the actual WVTR for Nitrile A glove isabout 25% less than predicted—based on glove thickness.

In other words, the WVTR is not linearly proportional based on thicknessalone, and the material does not have a constant standardized WVTR.While the inventors should not be held to a particular theory ofoperation, the nitrile rubber medical exam gloves according to thepresent invention appear to have about 20% denser structure per unitvolume than one would usually expect from a mere decrease in thicknessof a comparable elastomeric film or membrane. As used here, “density”refers not to bulk density as is more common, but rather refers tomolecular density or order. It is believed that the nitrile-butadienerubber gloves of the present invention have a more highly orderedmolecular structure than other nitrile-butadiene rubber gloves. Notintending to be bound by theory, this is evidenced by the fact that theWVTR for a glove made according to the present invention is less thanproportional to its thickness, compared to other nitrile-butadienerubber gloves. In other words, the WVTR is not linearly proportionalbased on thickness alone, and the material does not have a constantstandardized WVTR. This may indicate a more finely ordered or denserstructure. The more tightly packed structure may contribute to thetopographical features of the elastomeric film membrane that we haveobserved.

Generally speaking, the nitrile-butadiene rubber medical exam gloves ofthe present invention exhibit Water Vapor Transmission Rates that arecomparable to the thinnest commercially available polyvinyl chloridemedical exam gloves, which may have WVTR values of about 350 g/m²/24 hrday. However, most polyvinyl chloride medical exam gloves have WVTRvalues that are lower.

Physical Properties

For elastic materials such as elastomeric medical exam gloves,force-strain properties refer to a direct measurement of how a materialelastically deforms or responds (i.e., stretches) in response to anapplied force, regardless of the thickness of the material. The resultsof force strain testing are reported in units of force (e.g., Newtons orpounds-force) at a specified distance. Force-strain properties arefrequently referred to as “force-to-stretch”.

For elastic materials such as elastomeric medical exam gloves,stress-strain properties measure the response to an applied force perunit cross sectional area of the material. This property, sometimesreferred to as “modulus”, has dimensions of Force/Area and is measuredin units such as the Pascal or in units such as Newton per square meter(1 Pa=1 N/m²), dyne/cm², or pounds-force per inch squared (psi).

As used herein, the term “stretch-elongation” refers to the amount orpercentage that an elastomeric substrate or membrane is stretched orexpanded exceeding its original dimensions. The “percentage deformation”or “percentage elongation” can be determined according to the followingcalculation:Percentage Elongation=[(Final dimension−Initial dimension)/Initialdimension]×100

Similar to the nitrile-butadiene rubber materials described in U.S.Patent Publication Nos. 2006/0253956 (A1), and 2006/0257674 (A1), thecontents of which are incorporated herein by reference, the flexibilityand “softness” of an elastic membrane can be characterized by itsforce-to-strain value. For purposes of the present invention, thetesting and performance of elastic medical exam gloves will be reportedin terms of force-strain or “force-to-stretch” properties. Theforce-strain or “force-to-stretch” properties relate more directly toactual conditions of the medical exam gloves. The force-strain or“force-to-stretch” properties at a given thickness are particularlyimportant for thin gloves to have a comfortable force response becausenitrile-butadiene rubber formulations designed for thin gloves to havesufficient strength and barrier properties can result in a stiffer andless comfortable glove.

It is believe that softer and more flexible material is important for amedical exam glove to provide comfort provided the glove also exhibitssatisfactory levels of barrier performance. The nitrile-butadienemedical exam gloves of the present invention have force-to-stretch to agiven extension that compare favorably with medical exam gloves formedfrom natural rubber latex. The nitrile-butadiene medical exam gloves ofthe present invention have more comfortable levels of force-to-stretchto a given extension, particularly in comparison to conventionalpolyvinyl chloride medical exam gloves and thicker nitrile-butadienemedical exam gloves, as will be further illustrated below while alsoexhibiting satisfactory levels of barrier performance in comparison tothicker nitrile-butadiene medical exam gloves and superior levels ofbarrier performance in comparison to polyvinyl chloride medical examgloves as illustrated by pinhole defect testing. Importantly, thepresent invention provides these performance advantages in a practicaland economical way to combine the economic advantages of an inexpensivepolyvinyl chloride medical exam glove with a level of force-to-stretchperformance and barrier performance that compares favorably with moreexpensive and conventionally thicker nitrile-butadiene medical examgloves.

FIG. 5 is a comparative graph of the Force-Strain properties from fourdifferent samples of medical exam gloves made from synthetic materials.

One substrate is a conventional polyvinyl chloride medical exam gloveavailable as the Universal™ 3G Powder-Free Stretch Synthetic Exam Glovefrom Medline Industries, Inc. of Mundelein, Ill., (referred to as“Vinyl”) and three other substrates are: (1) a nitrile-butadiene rubberglove according to the present invention which had a thickness in thepalm region of the glove of approximately 0.05 millimeters as determinedby ASTM D3767, procedure A (referred to as “Nitrile A glove” or just“Nitrile A”); (2) a Kimberly-Clark® STERLING® nitrile medical exam glove(a nitrile-butadiene rubber glove which had a thickness in the palmregion of the glove of approximately 0.08 millimeters as determined byASTM D3767, procedure A (referred to as “Nitrile B glove” or just“Nitrile B”); and (3) a Kimberly-Clark® Safeskin® PURPLE Nitrile®medical exam glove (a nitrile-butadiene rubber glove) available fromKimberly-Clark Corporation which had a thickness in the palm region ofthe glove of approximately 0.11 millimeters as determined by ASTM D3767,procedure A (referred to as “Nitrile C glove” or just “Nitrile C”).

A comparison of the relative amounts of applied force (Newtons)necessary to stretch these nitrile rubber and vinyl-based gloves to 300%of an initial un-stretched dimension (length-wise) (F-300) is presentedin Table 3. Typical polyvinyl chloride medical exam gloves have athickness in the palm region of about 0.13-0.16 mm, and an applied forceat break of about 3.5-4.5 N, at a maximum strain, of about 440%elongation. The nitrile-butadiene rubber glove according to the presentinvention (Nitrile A glove) requires only an applied force of less thanor equal to about 1.5 N at about 300% strain and less than about 2 N atabout 400% strain, or about 2 N at about 500% strain. The amount offorce to stretch an elastic substrate sample, Nitrile A, with athickness ranging from about 0.03 mm to about 0.10 mm (more desirably, athickness ranging from about 0.05 mm to about 0.08 mm, and still moredesirably, a thickness ranging from about 0.055 to about 0.08 mm) rangesfrom about 1.08 N to about 1.45 N, with an average value of about 1.12 Nat about 0.07 mm.

The nitrile-butadiene medical exam gloves identified as the Nitrile Bglove and the Nitrile C glove, show a more pronounced difference. Theaverage amount of force applied to stretch 300% of an initial dimension(F-300) for the Nitrile B glove is about 1.77 N, and the average amountof force applied to stretch 300% of an initial dimension (F-300) for theNitrile C glove is about 2.47 N. For sake of comparison, a polyvinylchloride medical exam glove of similar thickness (˜0.08 mm) is moreresistant to stretching than either of the other nitrile-butadienerubber glove samples. The Universal™ 3G Powder-Free Stretch SyntheticExam Glove (i.e., Vinyl) requires an average F-300 of about 2.92 N—themost force to stretch—almost three times the force required for theNitrile A glove—the glove according to the present invention.

TABLE 3 Average Force to Stretch a Substrate to 300% of InitialDimensions (F-300) Average Thickness Average F-300 F-300 Range Sample(mm) (Newtons) (Newtons) Nitrile A 0.075 mm 1.12 N 1.06 N-1.48 N NitrileB 0.080 mm 1.77 N 1.56 N-2.20 N Nitrile C 0.113 mm 2.47 N 2.25 N-2.65 NVinyl 0.130 mm 2.92 N 2.80 N-3.10 N

The medical exam glove of the present invention may a force-strainresponse of a force (F300) of less than or equal to about 1.50 N atabout 300% strain. Typically, according to the invention, the medicalexam glove exhibits a force-response behavior that requires a force ofno more than about 1.45 N to stretch a test sample of the medical examglove with a thickness of about 0.03-0.10 mm to about 300% of aninitial, un-stretched dimension. Further, the medical exam gloveexhibits a force-strain response of a force of less than about 2 N atabout 400% strain, or about 2 N at about 500% strain. An elastomericglove according to the present invention having a thickness of betweenabout 0.05 to 0.10 mm in the palm region, desirably exhibits a force tobreak of less than 6.0 N or 6.5 N (desirably about 4N to about 6N), atan elongation at break of about 560 to about 630% of its originalun-stretched dimension. An elastomeric glove according to the presentinvention having a thickness of between about 0.05 to 0.10 mm in thepalm region, desirably exhibits a force to break of less than 6.0 N or6.5 N, at an elongation at break of about 600 to about 630% of itsoriginal un-stretched dimension.

A range of other physical properties were determined for variouscommercially available polyvinyl chloride medical exam gloves, for acommercially available nitrile-butadiene rubber medical exam glove, andfor an exemplary medical exam glove prepared in accordance with thepresent invention. The gloves are as follows:

Vinyl 1: MediGuard Vinyl Synthetic Powder-Free Exam Gloves availablefrom Medline Industries, Inc. of Mundelein, Ill.

Vinyl 2: Mediline Aloetouch® 3G Powder-Free Synthetic Exam Glovesavailable from Medline Industries, Inc. of Mundelein, Ill.

Vinyl 3: Universal™ 3G Powder-Free Stretch Synthetic Exam Gloveavailable from Medline Industries, Inc. of Mundelein, Ill.

Vinyl 4: Mediline Aloetouch® Ultra IC Powder-Free Stretch SyntheticCoated Exam Gloves available from Medline Industries, Inc. of Mundelein,Ill.

Vinyl 5: Cardinal Health Esteem® Stretchy Synthetic Powder-Free VinylExam Gloves available from Cardinal Health of Dublin, Ohio.

Vinyl 6: Cardinal Health InstaGard® PV Powdered Vinyl Exam Glovesavailable from Cardinal Health of Dublin, Ohio.

Nitrile A: nitrile-butadiene rubber medical exam glove according to thepresent invention

Nitrile B: Kimberly-Clark® STERLING® nitrile medical exam gloveavailable from Kimberly-Clark Corporation, Roswell, Ga. (anitrile-butadiene rubber glove referred to as “Nitrile B glove” or just“Nitrile B”)

The elongation at break and force at break properties were determined inaccordance with ASTM D412-06 utilizing the Die-D set of dimensions(Width dimension of the dumbbell specimen being 3 mm) using a samplesize of 10 gloves. The thickness of the glove (i.e., the single glovemembrane at the specified location) was determined in accordance withASTM D3767 for a sample size of 10 gloves. The weight of the glove andthe glove length, width at cuff and palm width was determined usingconventional techniques for a sample size of 10 gloves. The results oftesting are reported in Table 4 below:

TABLE 4 Comparative Properties of Polyvinyl Chloride Medical Exam GlovesTESTING VINYL 1 VINYL 2 VINYL 3 VINYL 4 VINYL 5 VINYL 6 NITRILE ANITRILE B Elongation at break (%) 443 445.3 447.4 506.4 421.1 357.1582.8 577.2 Force at break (N) 4.749 4.335 5.02 5.224 6.055 5.074 4.3387.935 Finger Thickness (mm) 0.121 0.097 0.123 0.129 0.135 0.104 0.08 0.1Palm Thickness (mm) 0.098 0.088 0.09 0.1 0.095 0.105 0.06 0.071 CuffThickness (mm) 0.054 0.062 0.065 0.097 0.058 0.073 0.05 0.065 Weight ofglove (g) 5.919 6.0108 6.5396 6.6011 6.395 6.4647 3.084 4.089 Length ofglove (mm) 249 247.1 248.7 239.5 240.2 232.3 239.8 237.3 Width at cuff(mm) 89.2 91.1 90.5 91 89.8 97.8 87.4 90.8 Palm width (mm) 95.4 97 97.398.6 98.1 95.4 96.2 95.5

Pinhole defect testing of nitrile-butadiene rubber medical exam glovesaccording to the present invention was conducted generally in accordancewith ASTM D5151-06 which is a “pass-fail” static water load testprocedure. Sample of gloves in lot sizes of about 100 gloves weretested. The accumulated totals of gloves tested exceeded severalthousand gloves (in some cases, several tens of thousands of gloves).The elastomeric glove according to the present invention had a failurerate of less than about 0.1 percent. In other words, less than 1 out1000 gloves exhibited a pinhole defect when subjected to pinhole defecttesting. The medical exam gloves of the present invention had a palmthickness as determined in accordance with ASTM D3767 averagingapproximately 0.053 mm.

Several commercially available nitrile-butadiene rubber medical examgloves were also tested generally in accordance with ASTM D5151-06 whichis a “pass-fail” static water load test procedure. The palm thickness ofthe gloves is determined in accordance with ASTM D3767 and an averagewas determined. The identity of the glove, the number of sample glovestested, the average palm thickness and the pinhole defect rate isreported below.

(1) Cardinal Esteem® Stretchy nitrile powder-free medical exam availablefrom Cardinal Health of Dublin, Ohio, average palm thickness: 0.13 mm,pinhole defect rate: 0.5%, 200 gloves tested.

(2) Medline Sensicare® Silk nitrile powder-free medical exam gloveavailable from Medline Industries, Inc. of Mundelein, Ill., palmthickness: 0.08 mm, pinhole defect rate: 3.8%, 600 gloves tested.

(3) Microflex UltraSense® nitrile powder-free medical exam gloveavailable from Microflex Corporation of Reno, Nev., palm thickness: 0.09mm, pinhole defect rate: 0.3%, 300 gloves tested.

(4) Sempermed Sempercare® Tender Touch nitrile powder-free medical examglove available from Sempermed USA, Inc. of Clearwater, Fla., palmthickness: 0.09 mm, pinhole defect rate: 2.3%, 1292 gloves tested.

(5) Medgluv Neutron Grey nitrile powder-free medical exam gloveavailable from Medgluv, Inc. of Miami, Fla., palm thickness: 0.07 mm,pinhole defect rate: 2.45%, 489 gloves tested.

These results show that commercially available powder-freenitrile-butadiene rubber medical exam gloves that are substantiallythicker than the gloves of the present invention have a significantlygreater pinhole defect rate. For example, the lowest pinhole defect rateof 0.3 percent is provided by a glove having art average palm thicknessof 0.09 mm that is approximately seventy percent (70%) greater than thepalm thickness of the glove of the present invention having a palmthickness of about 0.053 mm.

In certain embodiments, one may treat or coat the elastomeric substrate(e.g., either the inner donning surface or outer (grip) side of a gloveaccording to the present invention) with an antiseptic agent or odorant,such as citric acid, linalool, or lavender oil. Other nature orsynthetic scented extracts (e.g., lavender scent) may also be applied tothe substrate surface. The antiseptic agent may collect within thenumerous pores of the elastic film for slow release over time. The poresretard the antiseptic agent or odorant from being wiped off in use andincrease the likelihood that the active agent is retained. Theconcentrations of antiseptic or scent agents may range from about 0.001gram/cm² up to about 0.80 gram/cm². Typically, the amounts may rangefrom about 0.005 gram/cm² to 0.15 gram/cm²; more typically from about0.01 gram/cm² to about 0.05 or 0.07 gram/cm², inclusive.

Section—Experimental

I. Scanning Electron Microscopy (SEM) Imaging:

A small piece that was larger than about 1 millimeter squared (mm²) wascarefully removed from the grip sides of each glove and placed on thealuminum mounts using double-sided tape. The samples were mildly sputtercoated with gold to render electrical conductivity, then imaged in aJEOL JSM 6490LV scanning electron microscope. Two images were acquiredof each sample at 130× magnification which yields an area about 1millimeter squared (mm²), which is approximately the same area asscanned by the profilometer in the Non-Contact Profilometry analysisbelow. The images were taken using shadow mode backscatter imaging toclearly contrast the pores from the surface. These images were analyzedto obtain the average pore size and surface area percent coverage.

II. Non-Contact Profilometry:

Pieces of the grip sides were fixed to glass microscope slides usingsmooth double sided adhesive. The glove material was flattened onto theadhesive using mild pressure applied with a glass microscope cover slip.Optical scans were obtained using the FRT MicroProf® OpticalProfilometer using a 100-micrometer z-range white-light sensor which hasvertical resolution better than 10-nanometers and X-Y resolution ofapproximately 1 to 2 micrometers. The instrument is manufactured byFries Research & Technology, GmbH, having an office at Friedrich-EbertStrasse, 51429 Bergisch Gladbach, Germany

Two different 1 mm×1 mm areas were scanned with a sampling density of200 lines×200 points/line, giving data spacing of 5 micrometers in the Xand Y dimensions yielding approximately 40,000 data points for each 1mm×1 mm sample. The areas were pre-examined in a stereomicroscope toinsure that the surfaces appeared typical and were free of defects orcontaminant particles. The sample is fixed to the computer controlled XYstage which is scanned under the fixed optical sensor. The height ateach point is calculated based on the measured wavelength of thereflections.

The data were converted to Surface Data Format (.sdf) and analyzed usingMountains 2.2 programming. The universal roughness parameters Sa and Sqwere calculated and averaged. The total z-envelope height (St) was alsomeasured. St is not generally used or recognized as a measure of texturebut is a simple dimensional indicator.

Sa is the three-dimensional analogue of the 2D roughness parameter Ra,defined as the arithmetic average of the absolute values of the measureddeviations about the least-squares best fit plane through the data. Sqis the RMS calculation, which is more sensitive to larger deviations.These roughness parameters are universally recognized and may be used todefine differences.

III. Image Analysis and Moisture Vapor Transmission Rate:

Photomicrographs of the un-chlorinated grip-side surfaces of the NitrileA glove and the Nitrile C glove were made using the JEOL JSM 6490LVscanning electron microscope (SEM) at a linear magnification of 130×.The SEM photomicrograph images were analyzed using the LeicaMicrosystems QWIN Pro version 3.2.1 image analysis software (availablefrom Leica Microsystems of Heerbrugg, Switzerland) and the customwritten Quantimet User Interactive Programming System (QUIPS) algorithmreproduced below:

CONDITIONS = Jeol JSM 6490 SEM SET-UP & ACQUIRE IMAGECalibration (Local) Enter Results Header File Results Header (channel#1) File Line (channel #1) Image frame (x 0, y 0, Width 1280, Height960) Measure frame (x 33, y 47, Width 1215, Height 824) For (FIELD = 1to 2, step 1) PIN DETECTION AND IMAGE PROCESSING Read image [PAUSE](from file C:) Grey Transform (BSmooth from Image0 to Image1, cycles 1,operator Disc) Detect (blacker than 64, from Image1 into Binary0delineated) Binary Amend (Open from Binary0 to 1, Binary1, cycles 1,operator Disc, edge erode on) Binary Amend (Close from Binary1 toBinary2, cycles 2, operator Disc, edge erode on) Binary Amend (Open fromBinary2 to Binary3, cycles 1, operator Disc, edge erode on) BinaryIdentify (FillHoles from Binary3 to Binary4) MEASURE PIN AREA AND NUMBER(FIELD) Measure field (plane Binary4)    Selected parameters: Count,Area % File Field Results (channel #1) File Line (channel #1) FileLine (channel #1) MEASURE PIN SIZE DISTRIBUTION (FEATURE) Measurefeature (plane Binary4, 8 ferets, minimum area: 10, grey image: Image0)   Selected parameters: X FCP, Y FCP, Roundness, EquivDiam FeatureHistogram #1 (Y Param Number, X Param EquivDiam, from 1. to 100.,   logarithmic, 25 bins) Feature Histogram #2 (Y Param Number, X ParamRoundness, from 1. to 3.5, linear, 25    bins) Display Feature HistogramResults (#1, horizontal, differential, bins + graph (Y axis linear),statistics)    Data Window (1087, 801, 512, 359) Next (FIELD) FileFeature Histogram Results (#1, differential, statistics, bin details,channel #1) File Line (channel #1) File Line (channel #1) File FeatureHistogram Results (#2, differential, statistics, bin details, channel#1) File Line (channel #1) File Line (channel #1) Close File (channel#1) END

Two images were analyzed per code and the measurement region size ofeach was 0.6 mm². Spatial calibration for the image analysis wasperformed using the QWIN Pro system software and the micron bar locatedon the SEM images.

The QUIPS algorithm was used to read the digital SEM images,automatically detect the pore regions, perform image processing on thedetected binary regions, perform sizing measurements and export thedata, in the form of a histogram, directly to an EXCEL® spreadsheet.Data from each of the two images analyzed per code were accumulated intoa single equivalent-circular diameter (ECD) histogram.

Results showed that the Nitrile A glove sample had larger size pores asmeasured by equivalent-circular diameter (ECD) as well as over twice thepercentage of pore surface area relative to the Nitrile C glove sample.

Photomicrograph images acquired using the JEOL JSM 6490LV ScanningElectron Microscope were analyzed by image analysis for the size andcoverage of pores. FIG. 6A and FIG. 6B are scanning electron microscopy(SEM) photomicrographs, showing ‘raw’ and ‘detected’ pores,respectively, for an exemplary surface of an elastomeric glove accordingto the present invention. FIG. 7A and FIG. 7B are representative imagesshowing ‘raw’ and ‘detected’ pitting, respectively, for an exemplarycommercially available nitrile-butadiene rubber medical exam glove (aKimberly-Clark® Safeskin® PURPLE Nitrile® medical exam glove).

As can be observed from a comparison of the photomicrograph images, theNitrile A glove surface appears to have a larger number of pores whichcovered more of the surface. The percentage of the measured surface areacovered by pores, the equivalent circular diameter (ECD) of the pores asexpressed in micrometers and the pore count data is are shown in Table5.

TABLE 5 Coverage and Sizing Data of Nitrile- butadiene rubber gloveSurfaces % Pore ECD Sample ID Area (μm) S. Dev. Count/FOV Count/mm²Nitrile A 3.94 5.84 3.30 685 1153 Nitrile C 1.53 5.04 2.45 400 673

The data confirmed the visual observations in showing that the Nitrileglove surface had larger pores and a greater number of pores relative tothe Nitrile C glove surface. The percentage of pore surface areacoverage of the Nitrile A glove sample surface was well over double thepercentage of pore surface area coverage of the Nitrile C glove samplesurface.

FIGS. 8A and 8B are histograms illustrating the frequency of poreshaving a specified equivalent circular diameter as determined by opticalimage analysis described above. FIG. 8A illustrates the frequency ofpores having a specified equivalent circular diameter as determined byoptical image analysis for an exemplary surface of an elastomeric gloveaccording to the present invention (i.e., the Nitrile A glove). FIG. 8Billustrates the frequency of pores having a specified equivalentcircular diameter as determined by optical image analysis for anexemplary commercially available nitrile-butadiene rubber medical examglove (a Kimberly-Clark® Safeskin® PURPLE Nitrile® medical exam glove)which is referred to as the Nitrile C glove.

A Student's T analysis was performed on the ECD data at the 90%confidence level. The non-overlapping confidences ranges indicated thatthe mean values were different from each other and that Nitrile A gloveexhibits a higher mean pore size value that the Nitrile C glove. Forexample, the Nitrile A glove exhibits a pore size range of from about2.5 micrometers to about 27.5 micrometers and an average size 2-s range(2 standard deviations or 95%) of 13.2 micrometers. The Nitrile C gloveexhibits a pore size range of from about 2.5 micrometers to about 19.1micrometers and an average size 2-s range (2 standard deviations or 95%)of 9.8 micrometers.

FIG. 9 is a graph illustrating exemplary relationships between glovethickness and Water Vapor Transmission Rate for various samplenitrile-butadiene rubber gloves.

The Water Vapor Transmission Rate (WVTR) sometimes also called theMoisture Vapor Transmission Rate (MVTR) for the sample materials wasmeasured and calculated in accordance with ASTM Standard E96-80.Circular samples having a specified diameter were cut from each of thetest materials along with circular samples of the same diameter of aknown control material. Three samples were prepared for each material.The control sample was run with each test and the preliminary testvalues were corrected to set conditions based on the performance of thecontrol sample.

The present invention has been described both in general and in detailby way of examples. Persons skilled in the art will understand that theinvention is not limited necessarily to the specific embodimentsdisclosed. Modifications and variations may be made without departingfrom the scope of the invention as defined by the following claims ortheir equivalents, including equivalent components presently known, orto be developed, which may be used within the scope of the presentinvention. Hence, unless changes otherwise depart from the scope of theinvention, the changes should be construed as being included herein.

We claim:
 1. A process for making a single layer elastomeric glove,wherein the process is a single latex dip process, the processcomprising the steps of: coating a surface of a mold with a coagulantsolution and a release agent, wherein the release agent is emulsified inthe coagulant solution and is present in an amount of about 1 percent orless based on the weight of the coagulant solution, the coagulantsolution having a calcium ion concentration of between about 3 percentand about 5 percent based on the weight of calcium ions in the coagulantsolution; partially drying the mold coated with the coagulant solutionand release agent; immersing the partially dried mold into annitrile-butadiene rubber latex emulsion having a latex solids content ofbetween about 12 percent and about 20 percent, by weight, wherein theratio of coagulant ions on the mold and latex solids content isapproximately 1:4, for a dwell time of between about 7 seconds and 15seconds to form a layer of coagulated nitrile-butadiene rubber latex onthe mold surface; removing the mold from the nitrile-butadiene rubberlatex emulsion; immersing the mold containing the coagulatednitrile-butadiene rubber latex into an aqueous bath to remove excesscalcium ions and then drying the coagulated nitrile-butadiene rubberlatex to form a glove body on the mold; and removing the glove body fromthe mold by inverting the glove body such that an exterior surface ofthe glove body forms an interior surface of the elastomeric glove and aninterior surface of the glove body forms an exterior surface of theelastomeric glove, wherein the exterior surface of the elastomeric gloveis characterized by a pore density of greater than or equal to about 800pores per mm² as determined by optical image analysis, and wherein theglove body has a surface area to volume ratio in a range from 84/cm to400/cm.
 2. The process according to claim 1, wherein the latex solidscontent is between about 14 percent and about 20 percent, by weight. 3.The process according to claim 1, wherein the dwell time is betweenabout 8 seconds and 12 seconds.
 4. The process according to claim 1,wherein a nitrite-butadiene rubber latex emulsion for the elastomericglove comprises a terpolymer composition of acrylonitrile, butadiene,and carboxylic acid in which the acrylonitrile polymer content is about15 percent, by weight, to about 42 percent, by weight, the carboxylicacid content is between about 1 percent, by weight and about 10 percentby weight, and the remaining portion of the terpolymer composition isbutadiene.
 5. The process according to claim 1, further comprisingimmersing the mold containing the glove body into a chlorinating bath tochlorinate the exterior surface of the glove body on the mold prior toremoving the glove body from the mold.
 6. The process according to claim1, wherein the release agent is substantially uniformly distributed overthe exterior surface of the elastomeric glove, wherein the release agentis waxy.
 7. The process according to claim 1, wherein the exteriorsurface of the elastomeric glove has a Surface Root Mean SquareRoughness (Sq) of from about 3.00 μm to about 6.55 μm.
 8. The processaccording to claim 1, wherein the exterior surface of the elastomericglove has a Surface Root Mean Square Roughness (Sq) of from about 3.00μm to about 5.30 μm.
 9. The process according to claim 1, wherein theelastomeric glove has a failure rate of less than about 1 percent whenthe elastomeric glove is subjected to pinhole leak testing generally inaccordance with ASTM D5151-06.
 10. The process according to claim 1,wherein the elastomeric glove has a failure rate of less than about 0.5percent when the elastomeric glove is subjected to pinhole leak testinggenerally in accordance with ASTM D5151-06.
 11. The process according toclaim 1, wherein the elastomeric glove has a failure rate of less thanabout 0.1 percent when the elastomeric glove is subjected to pinholeleak testing generally in accordance with ASTM D5151-06.
 12. The processaccording to claim 1, wherein the single layer elastomeric glove has athickness in the palm region of about 0.05 mm to about 0.09 mm.